Not Applicable
Not Applicable.
This invention relates in general to rolling element bearings and, more particularly, to an integral race package bearing with an improved lubrication system that allows for cooler operation of the bearing.
Multiple row, rolling element bearing assemblies such as two-row and four-row rolling element bearings are required for certain applications in which greater bearing rating is needed within a limited space. A typical two-row tapered bearing 1 is shown in FIG. 1. The bearing 1 includes a cup carrier 3, bearing outer races or cups 5, tapered rollers 7, and inner races or cones 9. The cup carrier 3 includes a flange to connect or mount the bearing in an application. Typically, the cup carrier 3 for a multiple-row bearing is manufactured separately from the bearing cups 5, and the bearing cups which define the outer race against which the rolling elements rotate, are fitted into the cup carrier. As seen in FIG. 1, the bearing cups for the two rows of rolling elements are formed separately. Thus, there are two rings or bearing cups which are fitted into the cup carrier 3.
The manufacturing of the cup carrier separately from the bearing cups involves several problems or disadvantages. In particular, manufacturing a separate bearing cup carrier to the required tolerances is difficult. In addition, the separate bearing cup carrier requires that the customer perform additional assembly steps after delivery. Further, using separately manufactured parts results in a high tolerance stack-up, leading to larger and therefore less accurate bearing setting ranges that are unacceptable in many applications. As a result, using two single row assemblies to produce a multi-row bearing assembly can be time-consuming and inconvenient for the customer.
Using separate bearing components also complicates the required lubricant delivery in multiple-row bearings. In tapered roller bearings, the arrangement of the bearing components pumps lubricant out from the small end to the large end of the rollers. At higher rates of operating speed, the bearings have a tendency to pump themselves dry. In order for the bearings to operate successfully at higher rates of speed, lubricant must be pumped between the multiple rows of bearings using an external pumping system. The lubricant is typically delivered to the rollers 3 through a single port 11 which is in fluid communication with a plurality of radial holes 13 via a groove 15. However, lubrication solutions are limited in multiple-row bearings with separately manufactured components. With separately manufactured components, relatively little material remains in the bearing or cup carrier for adding lubrication enhancements such as additional or larger diameter lubrication holes without compromising component integrity.
A multi-row rolling element bearing assembly is provided for use in applications, such as differentials. The rolling element bearing assembly includes an inner race defining at least two inner raceways, an outer race defining at least two outer raceways, and a plurality of rolling elements positioned between the inner and outer raceways arranged in at least two rows. Although the bearing is described to have rollers, the rolling elements can be rollers, balls, or other types of rolling elements. The bearing assembly includes a novel lubrication system which reduces the maximum temperature attained by the bearing during operation of the bearing and the time spent at that maximum temperature.
The lubrication system includes a forced lubrication port or passage connectable to a forced lubrication system and a secondary lubrication port or passage. The forced and secondary lubrication ports define channels extending from an outer surface of the bearing assembly to the radial inner surface at a point near the rolling elements. A tertiary lubrication port or passage may also be provided. The forced lubrication system delivers lubricant to the bearing through the forced lubrication port.
When installed in a machine, the bearing is at least partially submerged in lubricant up to a desired level, to define a lubricant level. The secondary lubrication port is positioned below the lubricant level to be submerged in lubricant. Thus, the lubricant passively flows into the bearing through the secondary lubrication ports and the presence of the secondary lubrication ports maintains a substantially constant level of lubricant in the bearing to ensure lubrication of the rolling elements. The tertiary lubrication ports on the bearing are above the lubricant level. Any lubricant which is flung from nearby parts of the machine toward the bearing can enter the bearing through the tertiary lubrication ports.
The forced lubrication port and the secondary lubrication ports are preferably axial ports which are formed on either the front or back surfaces of the outer race, and which open along the inner surface of the outer race between the rolling elements. The tertiary port is preferably a radially extending port which is formed on the radial outer or side surface of the outer race and which opens along the inner surface of the outer race between the rolling elements.
Preferably, there is a single forced lubrication port or passage. The forced lubrication port or passage has only one entrance into the bearing and a single exit from the passage on the inner surface of the outer face. This is compared with the several holes in the prior art bearing through which lubricant is forced. The forced lubrication port is larger in diameter than the forced lubrication ports of prior art bearing assemblies. To facilitate the larger size of the forced lubrication port, as well as the secondary and tertiary ports, the outer race is formed as a one-piece, unitary element. It includes an integral flange to mount the bearing in the application. Additionally, the outer raceways are formed on the inner surface of the outer race. Hence, the use of separate bearing cups is eliminated. The elimination of separate bearing cups substantially reduces the tolerance stack up resulting from assembly of several parts. It also reduces the total cost of use. The actual cost of materials for the bearing assembly is not reduced substantially relative to the prior art bearing assemblies (such as shown in FIG. 1). However, due to the higher life and reliability of our new bearing assembly, and the less frequent replacement of the bearing assemblies, overall operating costs are decreased.